Somewhere on the web, there should be a compendium of useful (or near-useful) Perl Regular Expressions (also called patterns, regexes, and !REs). Does it already exist? Until we can link to a more authoritative list from this page, let's put them here.
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== Regexp::Common ==
The [=Regexp::Common] module provides some commonly-needed patterns. See http://search.cpan.org/~abigail/Regexp-Common-2.113/
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== The Patterns ==
Reader beware: Although we do our best to keep these accurate, the KwikiFormattingRules (and careless editing) may mangle some of these patterns. Use them at your own risk! (And help everybody out: Correct the bugs when you find them.)
These are somewhat modified from the perlfaq, section 4:
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Add more, please!